Transglutaminases (TGases) have been exploited for some time in the food industry for their ability to cross-link proteins. TGases have been shown to be capable of conjugating glutamine and lysine residues, including antibodies (see, e.g., Josten et al. (2000) J. Immunol. Methods 240, 47-54; Mindt et al (2008) Bioconjug. Chem. 19, 271-278; Jeger et al (2010) Angew. Chem. Int. Ed. 49: 9995-9997); Kamiya et al (2003) Enzyme. Microb. Technol. 33, 492-496 and U.S. patent publication no. 2011/0184147.
Conjugation of molecular markers and other moieties of interest to antibodies are of considerable commercial interest. However, the rules which govern selection by TGases of glutamine residues for modification are still largely unknown. Moreover, production process permitting highly controlled large scale and economically advantageous production of conjugated antibodies have not been reported. There is therefore a need in the art for improved methods to predictably moieties onto polypeptides using TGases.